The invention is a touch panel device which electrically indicates the X-Y coordinates of contact of an operator's finger on it and is sensitive to pressure only. Frequently, information is displayed on a substrate beneath the touch panel as well. The coordinates of a contact can be related to the displayed information thus providing for interactive communication between the operator and the device of which the touch panel forms a part.
The prior art includes a variety of techniques for sensing the location of contact on a surface. The most similar device of which the inventors are aware is the stretched drumhead type of membrane. This device employs a membrane spaced from a flat substrate and which can be deflected to cause conductors carried on it to contact those on the substrate. Another device is disclosed in an article entitled "CRT Touch Panels Provide Maximum Flexibility in Computer Interaction," Control Engineering, July 1976, pp. 33-34. This article discloses a curved flexible plastic sheet carrying small wires. The sheet can be deflected to cause these wires to come into contact with an orthogonal set of similar wires mounted immediately below. Spacers separate the sets of wires. U.S. Pat. No. 3,760,360 discloses a quite similar device embodied in a flat panel but having no capability of interactively displaying information. U.S. Pat. No. 3,495,232 discloses a somewhat simpler embodiment of a similar device. U.S. Pat. No. 3,921,167 discloses a panel location-sensitive to the approach of an external probe sensing change in capacitance.